(1) Field of the Invention
The present invention relates to an improvement of tire non-skid devices, which are used in the state that they are fitted to tires of vehicles for ensuring safe running on icy roads, snowy roads, etc.
(2) Related Art Statement
As measures for ensuring safe running on icy or snowy roads, there are well known stud tires in which studs made of a conventional hard alloy are studded directly into the tire. However, the stud tire has the shortcoming in that when it runs on a dry road, the studs rapidly wear. For instance, when a stud tire is subjected to a running test on a dry road, that is, when the stud tire with chrom-molybdenum steel studs is run on a general road at an average speed of 30 km/h for 1 hour, on a bad road at the average speed of 25 km/h for 30 minutes, and on an express highway at the average speed of 80 km/h for 30 minutes in the state that the tire is fitted to a passenger car having a displacement of 2,000 cc, the stud wears by as much as about 2 mm. Thus, its non-skid effect is greatly lowered. Further, such studs made of the above conventional metal are likely to be corroded with an anti-freezing agent or water present on the roads. If wearing and corrosion are co-existent, the wearing is promoted extremely. Thus, as shown in Japanese Patent Publication No. 59-14,364, it has recently been proposed that the conventional metal studs are replaced with those made of a ceramic material having excellent corrosion resistance and wear resistance. However, in this case, there still exists another problem as to the stud tires. That is, since it is not easy to attach or detach the stud tire to or from the wheel, it is actually impossible that the tire is briskly detached when it runs on the dry road unlike tire chains. This also provokes the above wearing problem.